1. Field of the Invention
The present invention relates to a pressure buffer for alleviating the fluctuation in pressure of ink supplied to an ink-jet recording head which is applied to a printer, a facsimile machine, and the like, and which performs printing with respect to a recording medium by jetting liquid droplets to the recording medium, and to an ink-jet recording apparatus with the pressure buffer mounted thereon.
2. Description of the Related Art
An ink-jet recording apparatus for recording characters and images on a recording medium by using an ink-jet recording head having a plurality of nozzles for discharging ink has been conventionally known. In such an ink-jet recording apparatus, it is necessary to minimize the fluctuation in pressure of ink supplied to the ink-jet recording head that causes a discharge failure when characters and images are recorded on a recording medium.
FIG. 4 shows a schematic view of an example of an ink-jet recording apparatus 100 provided with a pressure buffer for alleviating the fluctuation in pressure of ink supplied to an ink-jet recording head.
As shown in FIG. 4, in the prior art, the ink-jet recording apparatus 100 includes at least an ink container 101, a force-feed pump 102 for feeding ink from the ink container 101, an ink-jet recording head 103 for receiving the ink fed from the ink container 101 by the force-feed pump 102, and a pressure buffer 105 set on an ink supply path 104 between the force-feed pump 102 and the ink-jet recording head 103.
FIG. 5 shows a plan view of the pressure buffer 105, and FIG. 6 shows a cross-sectional view taken along a line â–â′ in FIG. 5 of the pressure buffer 105. The pressure buffer 105 includes a substrate 107 having a concave portion 106 and a connection flow path 108 communicated with the concave portion 106 and connected to the ink supply path 104 at both sides of the substrate 107. Furthermore, a flexible film 109 adheres to the substrate 107 so as to tightly close the concave portion 106 to constitute a chamber 118. Herein, a plurality of support pillars 110 projecting in the concave portion 106 do not adhere to the flexible film 109, and are detachable freely. A packing 112 having a through hole 111 opposed to the chamber 118 is provided outside of the flexible film 109 and an elastic member 113 is provided in the through-hole 111. Furthermore, a pressure plate 114 is provided outside of the packing 112, and a through hole 115 for air vent is provided at a position of the pressure plate 114 opposed to the chamber 118.
In order to fill the ink-jet recording head 103 with ink, the force-feed pump 102 is operated, ink is fed under pressure to the ink-jet recording head 103 in a direction represented by an arrow α shown in FIG. 4, and at this time, all the communicated elements from the ink container 101 to the ink-jet recording head 103 in FIG. 4 are filled with ink so that air bubbles do not remain inside the communicated elements. Furthermore, the ink-jet recording head 103 may be filled with ink by aspirating ink through a nozzle string (not shown) of the ink-jet recording head 103 with a negative pressure.
Furthermore, when the ink-jet recording head 103 is filled with ink that is fed under pressure, the pressure plate 114 suppresses the vibration of the flexible film 109. When the ink-jet recording head 103 is filled with ink that is aspirated with a negative pressure, the support pillars 110 also suppress the vibration of the flexible film 109. Furthermore, the elastic member 113 immediately attenuates the vibration of the flexible film 109.
When the pressure buffer 105 is assembled, the through hole 115 is indispensable for venting air remaining at a position of the flexible film 109 opposed to the chamber 118, and also is used as a window for identifying the ink filling situation of the chamber 118 (e.g., see Patent Document 1).
[Patent Document 1]
Japanese Patent No. 2873435 (pages 1–3, FIGS. 1 and 2)
In the pressure buffer of the prior art, there is the following description: when filling of ink under pressure is performed, the concave portion of the substrate provided in the pressure buffer is filled with the ink so that air bubbles do not remain in the chamber tightly closed with the flexible film.
However, when filling of ink under pressure is actually performed, an air layer is formed by remaining air bubbles compressed in the chamber, and when a compression action by pressure is eliminated after the completion of the filling of ink under pressure, the remaining air bubbles expand to push out the ink filling the chamber from the chamber and diffuse to an ink supply path in the vicinity of the pressure buffer.
When the ink-jet recording head is allowed to discharge ink in this state, the air bubbles diffusing to the ink supply path reach the ink-jet recording head, causing a discharge failure such as dropout.
In order to eliminate the above-mentioned cause, in the pressure buffer of the prior art, before filling of ink under pressure, it is necessary to perform filling of ink by aspiration via a nozzle string of the ink-jet recording head, and after remaining air bubbles in the chamber are removed completely, it is necessary to perform the filling of ink under pressure. Consequently, two filling mechanisms are required, which enlarges the ink-jet recording apparatus and increases a cost.
Furthermore, the pressure buffer of the prior art includes a through hole for air vent placed at a position of the flexible film opposed to the chamber, in the pressure plate outside of the pressure buffer. In the case where filling ink is UV-curable ink, there arises a problem in that light enters the chamber from outside of the pressure buffer to cure the UV-curable ink.